Active clusters in disordered systems

We introduce an exact algorithm to calculate the distribution of large low energy clusters (droplets) in disordered manifolds and disordered magnets,a nd we analyze die extent to which these clusters can be treated as independ ent two-level systems. We show that interfaces in randomly diluted networks always have broad droplet distributions, while diluted antiferromagnets in a field can have either power law or exponential droplet distributions. [S 1063-651X(99)08110-6].